Olivia: If you’ve ever had to take a drug test for sports or work, a well-meaning friend might have warned you to skip that poppy seed bagel for breakfast. It sounds like an urban legend, but poppy seeds might actually make you test positive for opiates – a group of highly-regulated or illegal drugs that can be really addictive.

Turns out, morphine and poppy seeds come from the same plant: the opium poppy. So it’s possible that a tiny, but detectable, amount of morphine or related chemicals might show up in a urine test, all because of an innocent-looking food.

Opium is a milky goo that’s naturally made in the opium poppy’s seed pods. This plant goop contains a lot of different alkaloids, which are a class of nitrogen-containing chemicals that have a lot of effects on the human body.

Some alkaloids can mimic or block different neurotransmitters, which are chemicals that bind to receptors in your brain. And this can affect how you perceive pain or euphoria, and can even lead to addiction. You might have heard of the alkaloid morphine, for instance. It’s found in opium, and it’s a powerful painkiller and precursor to the illegal drug heroin.

Poppy seeds don’t contain many or any alkaloids on their own, but they might get some chemical residue on them while they’re being harvested. The trace amounts of opiates that might end up in your poppy seed muffin won’t come anywhere close to a prescription dose of morphine, but urine tests that are designed to detect drugs are pretty sensitive.

The first step in a typical urine test is to check whether there’s any drug molecules at all. It’s called an immunoassay, because it uses antibodies, like the proteins in your immune system, to recognize specific molecules, like opiates. The antibodies are also engineered to make a detectable signal to say, “hey, there’s some chemical here!” If the immunoassay test comes up positive, the next step is to double-check those results, and see how much of each chemical there is in there.

For that, scientists can use a technique called gas chromatography-mass spectrometry, to separate and analyze different kinds of molecules. Abusing opiates would leave a lot more morphine in your system than just snacking on poppy seed muffins, so that’s why the concentration matters in a drug test.

In the 2000s in the U.S., the threshold for opiates in a urine sample was raised from 300 to 2000 nanograms per milliliter, to hopefully reduce false alarms from anything like poppy seeds. Still, if you’re about to take a drug test, it might not hurt to eat a nice, safe blueberry bagel with your morning coffee... just in case.

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